The present invention relates to an arrangement for determination of angle of rotation of two rotating parts.
For control and regulation of internal combustion engines, especially for an electronic ignition and injection, it is necessary to know both the position of the crankshaft and the camshaft. It is known to scan a measuring wheel connected with the camshaft and provided with a signal marking by a so-called phase signal sensor which is an inductive, optical or Hall sensor and arranged in the ignition distributor or on the camshaft. In addition to the phase signal sensor, a second sensor is utilized, which scans a disc connected with the crankshaft of an internal combustion engine. Conventionally, a plurality of identical marks and also a distinguishable mark is provided on the disc. The rotational speed is determined by similar marks, which the distinguishable mark is used for generation of a reference mark signal. The above arrangement can determine the position of the crankshaft as well as the camshaft and thereby the position of both shafts relative to one another. Therefore cylinder discrimination is possible which is required for electrical ignition. Such an arrangement is disclosed, for example, in the German Published Patent Application DE-OS 3,307,833.
The known arrangement has however the disadvantage that it is very expensive. The reason is that it requires two independent sensors. It is costly and there is the danger that during rough operation of the internal combustion engine one or both sensors can fail.
Other arrangements of the above-mentioned type are also known. In known arrangements the positions of two rotatable parts can be determined and for each part an individual sensor is provided. For example, the device disclosed in German Patent document 4,038,413 is used for determination of a torque applied to a shaft, in which two increment wheels connected with the shaft are scanned. Torque is determined from their rotation relative to one another.